Aldehydes and ketones II: Enolates *

Question 1

The carbon adjacent to the carbonyl carbon is the

Answer 1

alpha carbon

Question 2

the hydrogen attached to the alpha carbon is the

Answer 2

alpha hydrogen

Question 3

Alpha hydrogens are relatively

Answer 3

acidic and can be removed by a strong base. The electron-withdrawing oxygen of the carbonyl weakens the C-H bonds on the alpha carbon. Enolate resulting from the deprotonation can be stabilized by resonance with the carbonyl.

Question 4

ketones are less reactive towards nucleophiles because of the

Answer 4

steric hindrance and alpha carbanion destabilization. The presence of an additional alkyl group crowds the transition step and increases its energy. The alkyl group also donates the electron density to the carbanion, making it less stable.

Question 5

aldehydes and ketones exist in the traditional ___ and in the less common ___ form.

Answer 5

keto form (C=O) . Enol form (ene +ol = double bond = hydroxyl group)

Question 6

tautomers

Answer 6

are isomers that can be interconverted by moving the hydrogen and a double bond. The keto and enol forms are tautomers of each other.

Question 7

The enol form can be deprotanated to form an

Answer 7

enolate. Enolates are good nucleophiles .

Question 8

Michael addition

Answer 8

an enolate attacks an alpha, beta- unsaturated carbonyl, creating bond.

Question 9

kinetic enolate

Answer 9

is favored by fast, irreversible reactions at lower temperatures with strong sterically hindered bases.

Question 10

thermodynamic enolate

Answer 10

is favored by slower, reversible reactions at higher temperatures with weaker, smaller bases .

Question 11

enamines

Answer 11

are tautomers of imines. like enols, enamines are less common tautomer.

Question 12

Aldol condensation

Answer 12

the aldehyde or ketone acts as both nucleophile and electrophile, resulting in the formatio of a carbon-carbon bond in a new molecule called an aldol.

Question 13

aldol

Answer 13

contains both aldehyde and alcohol functional groups .

Question 14

Nucleophile in aldol condensation

Answer 14

is the enolate formed from the deprotanation of the alpha-carbon.

Question 15

The electrophile of the aldol condensation

Answer 15

the aldehyde or ketone in the form of the keto tautomer

Question 16

condensation reaction

Answer 16

occurs in which the two molecules come together.

Question 17

dehydration reaction in aldol condensation

Answer 17

once the aldol is formed, a loss of water molecules occurs. The results in an alpha, beta unsaturated carbonyl

Question 18

retro aldol reactions

Answer 18

are in the revers of aldol condensation. Retro-aldol reactions are catalyzed by heat and base. In these reactions, the bonds between an alpha and beta carbon is cleaved.